1. Field of the Invention
This invention relates to improvements in the zoom lens barrel of a photographic camera, and more particularly to a zoom lens barrel whose forwardmost group lens is slidingly operated in the direction of the optical axis during focusing and/or zooming.
2. Description of the Prior Art
A mount on which accessories such as an optical filter and a lens hood can be mounted is usually provided on the object side end of the objective lens barrel of a camera. This mount is formed integrally with a ring for holding the foremost group lens and the position of the mount is displaced with the movement of the foremost group lens in the direction of the optical axis. The movement of the lens is accomplished by displacing a holding ring by an operating ring provided on the outer periphery of the lens barrel, and if the lens barrel is designed such that the operating ring is moved in the direction of the optical axis, it is preferably, for appearance, that the mount on which accessories are mounted and the operating ring be moved together. Further, among the accessories that may be mounted on the mount is a polarizing filter which has directionality about the optical axis, and therefore it is necessary that the displacement of the mount not involve rotation.
Thus is also known a zoom lens barrel designed to accomplish focusing by rotating operation of a single operating ring about the optical axis and to accomplish zooming by sliding operation of the single operating ring in the direction of the optical axis, but there is no known zoom lens barrel which satisfies the above-mentioned two conditions.